Hydraulic lift assist for tractor towed earth moving apparatus

ABSTRACT

The present invention includes hydraulic systems designed to allow the selection of a source of pressurized hydraulic fluid to lift a load. In one embodiment, a hydraulic system in accordance with the present invention comprises a hydraulic accumulator that may be selected as a source of pressurized hydraulic fluid to lift a load. Such a hydraulic system may or may not be part of a cushion ride system. The present invention also includes methods for selecting a source of pressurized hydraulic fluid to lift a load and earth moving or ground leveling apparatus that allow the selection of a source of pressurized hydraulic fluid to lift a load.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/661,703, filed Mar. 15, 2005, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to hydraulic systems for lifting a load. More specifically, the present invention relates to hydraulic systems that allow the selection of a secondary source of hydraulic power to lift a load.

BACKGROUND

Certain kinds of earth moving equipment use a single power source for multiple purposes. For instance, a tractor may use its internal combustion engine to not only provide locomotion, but to also operate a high pressure hydraulic pump. While the tractor engine is typically able to provide sufficient horsepower for all needs, there may arise situations where the tractor engine is under powered.

One example might include a tractor being used to pull an earth moving apparatus. As the tractor pulls the earth moving apparatus, it fills with earth thereby increasing the resistance to the tractor pull. In order to compensate for this increased resistance, the operator of the tractor may gradually lift the frame of the earth moving apparatus, and, thereby the cutting blade, as the apparatus fills with earth. This lifting of the cutting blade, using the tractor's hydraulic system, decreases the resistance to the tractor's pull as the blade cuts less deeply into the earth. However, because the earthmoving apparatus' hydraulic system is powered by the tractor's engine, the horsepower of the engine must now be split between the simultaneous pulling of the earth moving apparatus and the lifting of the cutting blade. If the tractor is in a heavy pull, operating the hydraulics to lift the cutting blade may put enough extra drag on the engine to cause it to stall.

Many hydraulic systems for lifting loads, such as an earth moving apparatus frame and/or cutting blade, are known. Such hydraulic systems typically use hydraulic pressure to actuate a hydraulic cylinder in such a way that a load is lifted. However, if the primary source of pressurized hydraulic fluid fails or is unable to provide sufficient hydraulic pressure, the system will be unable to lift the load.

A number of systems exist to provide hydraulic pressure given the absence, or failure, of a primary source of pressurized hydraulic fluid. Representative examples include, without limitation, the hydraulic systems disclosed in U.S. Pat. Nos. 5,313,795, 5,090,495, 3,965,587, 4,360,187, 5,037,368, 5,516,070, 5,806,838, 3,945,685, and 3,945,691, the disclosures of each which are hereby incorporated by reference. These systems typically use a hydraulic accumulator to store hydraulic pressure to be used in the absence or failure of another power source. Systems of this type are typically constantly engaged to the active hydraulic system with the accumulator being ‘inline’ between the sources of pressurized hydraulic fluid and the ultimate use. Such systems can be said to be ‘constantly engaged’ as the operator of the system has no means of selecting when the pressure stored in the accumulator is not to be used, i.e. no means of disconnecting the accumulator from the hydraulic system. As such, the constant engagement of such systems do not allow the operator or designer of the hydraulic system to select whether the primary source of pressurized hydraulic fluid or the reserve hydraulic pressure in the accumulator is to be used for a given purpose. The reserve pressure is always available regardless of the operator's wishes. However, the hydraulic systems typical of earth moving machinery are designed so as to not be under significant pressure unless they are being used. Thus, a ‘constantly engaged’ accumulator would provide hydraulic pressure to the system every time the primary source is not in use, even when the operator desires that there be relatively little hydraulic pressure in the system.

Other systems for selectively engaging an accumulator with a hydraulic system only engage when the hydraulic pressure in the system falls below a predetermined level. Representative examples include, without limitation, the hydraulic systems disclosed in U.S. Pat. Nos. 4,736,991, and 4,792,192, the disclosures of each which are hereby incorporated by reference. However, such selective engagement systems are of little aid in selectively raising an earth moving apparatus frame, bucket, or cutting blade. This is because the hydraulic systems typical of earth moving machinery are not under significant pressure unless they are being used. Thus, an accumulator under a pressure sensitive control provides hydraulic pressure to the system every time the primary source is not in use, precisely when the operator desires that there be relatively little hydraulic pressure in the system.

Lastly, accumulator systems that engage when a certain back pressure has been reached are also known. A representative example includes, without limitation, the hydraulic system disclosed in U.S. Pat. No. 2,846,187, the disclosure of which is hereby incorporated by reference. In such a system, the hydraulic pressure in an accumulator is released into a hydraulic system when the pressure in the hydraulic system rises to a predetermined level. Such systems increase the hydraulic flow, allowing the hydraulic system to actuate more quickly, but would be of little use where the primary source of hydraulic power is unable to provide that predetermined hydraulic pressure. Further, such systems do not allow the operator or designer of the hydraulic system to select whether the primary source of pressurized hydraulic fluid or the reserve hydraulic pressure in the accumulator is used.

As such, an improved hydraulic system that allows the selective introduction of a reserve source of pressurized hydraulic fluid to lift a load would be an improvement in the art.

SUMMARY

The present invention includes hydraulic systems designed to allow the selection of a source of pressurized hydraulic fluid to lift a load. In one illustrative embodiment, a hydraulic system in accordance with the present invention comprises a hydraulic accumulator that may be selected as a source of pressurized hydraulic fluid to lift a load. Such a hydraulic system may or may not be part of a cushion ride system.

The present invention also includes methods for selecting a source of pressurized hydraulic fluid to lift a load. In one illustrative embodiment, a source of pressurized hydraulic fluid is used to charge an accumulator. The hydraulic pressure in the accumulator is then used to lift the load when selected to do so.

A further illustrative embodiment of the present invention includes a hydraulic system comprising a hydraulic accumulator that may be selected as a source of pressurized hydraulic fluid to lift a load into earth moving or ground leveling apparatus. The load lifted in the earth moving apparatus may be the earth moving or ground leveling apparatus frame, wheels, apron, cutting blade or other portion of the earth moving or ground leveling apparatus or its cargo. Such a hydraulic system may or may not be part of a cushion ride system incorporated into the earth moving or ground leveling apparatus.

DESCRIPTION OF THE DRAWINGS

It will be appreciated by those of ordinary skill in the art that the elements depicted in the various drawings are not to scale, but are for illustrative purposes only. The nature of the present invention, as well as other embodiments of the present invention may be more clearly understood by reference to the following detailed description of the invention, to the appended claims, and to the several drawings attached hereto.

FIG. 1 is a schematic diagram of an illustrative embodiment of a hydraulic system for selectively regulating the flow of a hydraulic fluid into and out of a hydraulic accumulator.

FIG. 2 is a schematic diagram of a second illustrative embodiment of a hydraulic system for selectively regulating the flow of hydraulic fluid between a source of pressurized hydraulic fluid, a hydraulic accumulator, a hydraulic cylinder, and a cushion ride system.

FIG. 3 illustrates a further embodiment of an earth moving apparatus on to which the hydraulic system of the present invention may be incorporated.

DETAILED DESCRIPTION

It will be appreciated that the embodiments described herein, while illustrative, are not intended to so limit the invention or the scope of the appended claims. Those of ordinary skill in the art will understand that various combinations or modifications of the embodiments presented herein maybe made without departing from the scope of the present invention.

Referring now to drawing FIG. 1, there is illustrated a schematic view of a hydraulic system in accordance with the present invention generally at 100. As illustrated, the hydraulic system 100 comprises a source of pressurized hydraulic fluid generally at 102. The source of pressurized hydraulic fluid generally at 102 includes, as illustrated, a hydraulic pump 104, a reservoir of hydraulic fluid 106, a selector valve 108, and an engine 109 for driving hydraulic pump 104. A non-limiting example of a source of pressurized hydraulic fluid generally at 102 would be the engine and high pressure hydraulic system present on a prime mover. Examples of prime movers include, but are not limited to, tractors, trucks, and various other self-propelled vehicles. Hydraulic system 100 further comprises hydraulic lines 110 a and 110 b, which may be used to carry hydraulic fluid to and from hydraulic cylinders 112 a and 112 b. Branching from hydraulic line 110 a is a lift assist system generally at 114. The lift assist system generally at 114 includes an accumulator 116, a check valve 118, a valve 120, and a check valve 122. As shown, the directional force of the load on hydraulic cylinder 112 a is as indicated by arrow 124.

Although not illustrated, the hydraulic system 100 may also be used to operate multiple hydraulic cylinders which can be single or double acting. Such additional cylinders may include, for example, but are not limited to, cylinders for raising or lowering a scraper bucket, opening or closing a scraper apron, operating a load ejector, operating a brake system, or providing pilot pressure for other hydraulic valves. These other operative hydraulic systems are as illustrated and disclosed in U.S. Pat. Nos. 4,383,380, 4,388,769, 4,398,363, 4,553,608, and 6,347,670 to Miskin which are incorporated herein by reference.

During normal operation, valve 120 remains closed. As hydraulic cylinders 112 a and 112 b are actuated during normal operation, hydraulic oil under pressure will pass through check valve 118 to be stored in accumulator 116. If the operator desires, or if a certain predetermined condition or conditions are sensed, valve 120 may be caused to open allowing the stored hydraulic oil under pressured to pass through valve 120 and check valve 122 and into hydraulic line 110 a. If the stored hydraulic pressure in accumulator 116 is sufficient, hydraulic cylinders 112 a and 112 b will actuate to lift the load. When actuating the hydraulic cylinder causes the lifting of a load comprising the frame of an earth moving apparatus, bucket, and/or cutting blade, the demands on engine 109 may be thereby reduced, allowing the source of pressurized hydraulic fluid generally at 102 to further lift the load without assistance of the hydraulic pressure stored in the accumulator.

It will be appreciated by one of skill in the art that various types of valve 120 may be used. In one exemplary embodiment, valve 120 may comprise an electrically-controlled, solenoid-type valve that may be controlled by a control switch (not shown) that may be located in the cab of the prime mover used to pull the apparatus to which hydraulic system 100 is mounted, or, if the apparatus on which hydraulic system 100 is self-propelled, the control switch (not shown) may be located in the control area of the self-propelled apparatus. In other embodiments, valve 120 may be any type of hydraulic valve and controlled in any manner known in the art, such as by mechanical systems and the like. Other types of valves that may be used with hydraulic system 100 of the present invention include, without limitation, sandwich valves, hydraulic control valves, electro-hydraulic valves, remote control valves, mobile valves, directional control valves, check valves, glove valves, gate valves, and other types of manual control valves. Types of control systems that may be used to control valve 120 of the present invention include, without limitation, pressure controlled systems, pneumatic systems, vacuum systems, electronically controlled systems, automatically controlled systems, manually controlled systems, remote control systems, and mechanically linked systems.

As would be apparent to one of skill in the art, a load comprises the force of gravity acting on a particular mass so as to drive the actuation of a piston rod of a hydraulic cylinder. In one exemplary embodiment, the load may be the weight of the frame of an earth moving apparatus. The lifting of a load comprises the actuation of a hydraulic cylinder causing a load to move against the force of gravity.

Referring now to drawing FIG. 2, there is illustrated a schematic view of a hydraulic system in accordance with the present invention generally at 200. As illustrated, the hydraulic system 200 includes a cushion ride system generally at 210 in place of check valve 118. When actuated, the cushion ride system utilizes the accumulator 116 as a shock absorber when the hydraulic system 200 is mounted on a vehicle such as an earth moving or ground leveling apparatus. Examples of using an accumulator as a shock absorber can be found in U.S. Pat. Nos. 6,382,326 and 6,749,035, both of which are incorporated herein by reference. As illustrated, cushion ride system generally at 210 may comprise check valves 212 and 214, valves 216 and 220, and restrictor 218. Also depicted is valve 222. During normal operation, valve 222 remains open. However, if it desired to charge accumulator 116 without actuating hydraulic cylinders 112 a and 112 b, valve 222 may be closed, thereby diverting the flow of pressurized hydraulic away from hydraulic cylinders 112 a and 112 b.

Hydraulic system 200 further includes sensor 224 for sensing the flow of hydraulic fluid in hydraulic line 110 a. As shown, sensor 224 may be operatively connected to valves 120 and 220 so as to control the position of valves 120 and 220 in response to predetermined sensor inputs. It will be appreciated by one of skill in the art that the position and type of sensor 224 described is merely exemplary and that any number of sensors inputs may be used to determine when valves 120 and 220 are opened. Such sensors or inputs include, but are not limited to, operator decision, a system for sensing a failure of movement of hydraulic cylinders 112 a and 112 b when selector valve 108 is actuated so as to lift the load, a speed sensor for sensing the speed of the prime mover, a system for sensing the engine speed of a prime mover, a system for sensing which gear the transmission of the prime mover is currently in, or a system for sensing a lack of hydraulic fluid flow in hydraulic line 110 a when selector valve 108 is actuated so as to lift the load.

At the beginning of normal operation, valves 120 and 220 are opened and valve 222 closed so that hydraulic fluid under pressure from the source of pressurized hydraulic fluid generally at 102 can pass through valves 216 and 220 as well as check valve 212 and/or restrictor 218 to be stored in accumulator 116. Once the accumulator 116 is charged, valves 120 and 220 are closed and valve 222 is opened. If, at any time, the stored pressurized hydraulic fluid in accumulator 116 is selected to actuate hydraulic cylinders 112 a and 112 b, valves 120 and 220 will be opened and the hydraulic fluid will pass through restrictor 218 as well as valves 120 and 220 and into hydraulic line 110 a. If the stored hydraulic pressure in hydraulic accumulator 116 is sufficient, hydraulic cylinders 112 a and 112 b will be actuated to lift the load. To recharge accumulator 116, valve 222 may again be closed while valves 120 and 220 remain open to allow hydraulic fluid under pressure from the source of pressurized hydraulic fluid generally at 102 to pass into the accumulator. In the alternative, the accumulator may be recharged when piston rod 318 reaches its maximum extension while valves 120 and 220 remain open. To operate the cushion ride system, the operator interrupts the connection between hydraulic lines 110 a and 110 b and hydraulic pump 114 using selector valve 108. Valves 216 and 220 are then opened. Any forces on hydraulic cylinders 112 a and 112 b are then dampened by the entry and release of hydraulic fluid from accumulator 116.

Referring now to drawing FIG. 3, which is a side view of an earth moving apparatus generally at 300. Scrapers and earthmoving apparatuses of the general type to which earth moving apparatus 300 relate are generally known. Representative examples of earthmoving apparatuses include, without limitation, the scrapers disclosed in U.S. Pat. Nos. 4,383,380, 4,388,769, 4,398,363, 4,553,608, and 6,347,670 to Miskin, the disclosures of which are herein incorporated by reference. A typical earth moving apparatus includes a bucket for holding earth. The bucket includes a floor, a rear wall, two upstanding opposing side walls, an open front, and an open top. An apron, or gate, is located opposite the rear wall of the bucket and can swing closed to hold the soil in the bucket during transport. In a scraper device, a blade is located adjacent the front edge of the floor of the bucket and cuts the earth to a predetermined depth as the earth moving apparatus is moved forward over the earth's surface. The soil cut from the earth by the blade is collected in the bucket. When the bucket is full of soil, the earth moving apparatus is transported to another location where the soil is deposited. Other examples of earth moving apparatuses having a bucket include, but are not limited to, dump trucks, backhoes, and front end loaders.

More specifically, the depicted exemplary earth moving apparatus generally at 300 includes a frame 302, a cutting blade 304, a bucket 306, an apron 308 a tongue 310 and at least two ground engaging wheels 312. An actuator, such as hydraulic cylinder 112 a has a first end 314 and a second end 316. When a piston rod 318 of the hydraulic cylinder 112 a is extended (as shown), the frame 302 is effectively raised. The imposed weight of frame 302 thus applies pressure upon the piston rod of hydraulic cylinder 112 a. According the present invention, the pressure stored in accumulator 116 (not shown) may be used extend piston rod 318 of the hydraulic cylinder to effectively raise the frame 302 and therefore the bucket 306 and the cutting blade 304.

When beginning an earth scraping operation using an earth moving apparatus such as the an earth moving apparatus generally at 300, the operator first lifts the frame 302 by supplying hydraulic pressure to hydraulic cylinders 112 a and 112 b through hydraulic line 10 a by the selection of the proper setting of selector valve 108. The charging of the hydraulic accumulator 116 would occur automatically when the piston rod 318 is fully extended, if the hydraulic system is equipped with a check valve 118, or, if the earth moving apparatus 300 is equipped with a cushion ride system, such as the cushion ride system generally at 210, the accumulator can be charged when piston rod 318 reaches its maximum extension and valves 120 and 220 are opened or when valve 222 is closed and valves 120 and 220 are opened.

During normal operation, as the bucket 306 fills with earth, the resistance to the pull of the prime mover will increase. To mitigate this increased resistance, the operator or a sensor input may select to raise the frame 302, and thereby bucket 306 and cutting blade 304. However, if the tractor is in a heavy pull, engine 109 may not have enough power to both pull earth moving apparatus 300 and provide sufficient hydraulic pressure via hydraulic pump 104 to lift frame 302, and thereby bucket 306 and cutting blade 304. To provide sufficient hydraulic pressure, the operator or a sensor input from as sensor such as sensor 224 causes valves 120 and 220 to open releasing the hydraulic pressure stored in hydraulic accumulator 116, through valves 120 and 220, and into hydraulic line 110 a. If the hydraulic pressure stored in hydraulic accumulator is sufficient, piston rod 318 of hydraulic cylinder 112 a will be extended, raising the frame 302, and thereby bucket 306 and cutting blade 304. The resistance to the pull of the prime mover will be thereby decreased allowing the engine 109 to provide enough power to both pull earth moving apparatus 300 and provide sufficient further hydraulic pressure via hydraulic pump 104 to lift frame 302, and thereby bucket 306 and cutting blade 304. If the hydraulic system is equipped with a check valve 118 the accumulator 116 will be recharged when piston rod 318 reaches its maximum extension, or, if the earth moving apparatus 300 is equipped with a cushion ride system, such as the cushion ride system generally at 210, the accumulator may be recharged when piston rod 318 reaches its maximum extension and valves 120 and 220 are opened or when valve 222 is closed and valves 120 and 220 are opened.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are not intended to limit the scope of the present invention. Various combinations and modifications of the embodiments described herein may be made without departing from the scope of the present invention and all modifications are meant to be included within the scope of the present invention. Thus, while certain exemplary embodiments and details have been described for purposes of describing the invention, it will be apparent to those of ordinary skill in the art that various changes in the invention described herein may be made without departing from the scope of the present invention, which is defined in the appended claims. 

1. A hydraulic system for lifting a load, comprising: a hydraulic accumulator; a hydraulic cylinder situated to lift a load upon actuation; and one or more valves controlling the entry and exit of hydraulic fluid from the hydraulic accumulator, wherein at least one of the one or more valves is operatively disposed between the hydraulic accumulator and the hydraulic cylinder situated to lift a load and allowing for the non-selection of the accumulator as a source of hydraulic fluid to actuate the hydraulic cylinder situated to lift the load.
 2. The hydraulic system of claim 1, wherein the at least one of the one or more valves is an operator controlled valve.
 3. The hydraulic system of claim 1, wherein the at least one of the one or more valves is controlled by a sensor.
 4. The hydraulic system of claim 3, wherein the sensor is selected from the group consisting of a sensor for indicating the movement of the hydraulic cylinder situated to lift a load, a sensor for sensing the speed of a vehicle on which the apparatus is mounted, a sensor for sensing which gear a transmission of a prime mover is currently engaged, a sensor for sensing the engine speed of a prime mover, and a sensor for sensing the flow of hydraulic fluid to or from the hydraulic cylinder situated to lift a load.
 5. The hydraulic system of claim 1, further comprising a cushion ride system.
 6. The hydraulic system of claim 5, wherein the wherein the cushion ride system comprises a second hydraulic accumulator.
 7. The hydraulic system of claim 1, where the load comprises a bucket of an earth moving apparatus.
 8. The hydraulic system of claim 1, further comprising a source generating pressurizing hydraulic fluid in operative connection to the accumulator, the source located on a separate prime mover.
 9. An earth moving apparatus comprising: a hydraulic accumulator; a hydraulic cylinder situated to lift a frame of an earth moving apparatus, the hydraulic cylinder operatively connected to the hydraulic accumulator; and a valve disposed between the hydraulic accumulator and the hydraulic cylinder for controlling the flow of hydraulic fluid from the hydraulic accumulator to the hydraulic cylinder situated to lift a frame of the earth moving apparatus.
 10. The earth moving apparatus of claim 9, wherein the earth moving apparatus comprises an earth moving scraper.
 11. The earth moving apparatus of claim 9, wherein the earth moving apparatus further comprises structures for operatively connecting to a source of pressurizing hydraulic fluid located on a separate prime mover.
 12. The earth moving apparatus of claim 9, wherein the valve is an operator controlled valve.
 13. The earth moving apparatus of claim 9, further comprising a sensor associated with the hydraulic system of the earth moving apparatus.
 14. The earth moving apparatus of claim 13, wherein the valve is controlled by the sensor.
 15. The earth moving apparatus of claim 14, wherein the sensor is selected from the group consisting of a sensor for indicating the movement of the hydraulic cylinder situated to lift a scraper frame, a sensor for sensing the speed of the earth moving apparatus, a sensor for sensing which gear a transmission of a prime mover is currently engaged, a sensor for sensing the engine speed of a prime mover, and a sensor for sensing the flow of hydraulic fluid to or from the hydraulic cylinder situated to lift a frame of the earth moving apparatus.
 16. The earth moving apparatus of claim 9, further comprising a cushion ride system.
 17. The earth moving apparatus of claim 16, wherein the wherein the cushion ride system comprises a second hydraulic accumulator.
 18. An improved earth moving or ground leveling apparatus having a frame with opposing sides, at least two ground engaging wheels supporting the frame, and a bucket with a floor and a pair of sidewalls, the improvement comprising: a hydraulic accumulator; a hydraulic cylinder situated to lift the bucket; and one or more valves controlling the entry and exit of hydraulic fluid from the hydraulic accumulator, wherein at least one of the one or more valves is operatively disposed between the hydraulic accumulator and the hydraulic cylinder situated to lift the bucket and allowing for the non-selection of the accumulator as a source of hydraulic fluid to actuate the hydraulic cylinder situated to lift the bucket.
 19. The improved earth moving or ground leveling apparatus of claim 18, wherein the at least one of the one or more valves is an operator controlled valve.
 20. The improved earth moving or ground leveling apparatus of claim 18, wherein the at least one of the one or more valves is controlled by a sensor.
 21. The improved earth moving or ground leveling apparatus of claim 20, wherein the sensor is selected from the group consisting of a sensor for indicating the movement of the hydraulic cylinder situated to lift a scraper frame, a sensor for sensing the speed of the earth moving apparatus, a sensor for sensing which gear a transmission of a prime mover is currently engaged, a sensor for sensing the engine speed of a prime mover, and a sensor for sensing the flow of hydraulic fluid to or from a hydraulic cylinder of the earth moving or ground leveling apparatus. 